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<H1>deleteffc(?Var, +List, -Rest)</H1>
Select from List the variable Var which has the smallest domain and most
constraints and return the rest of the list.


<DL>
<DT><EM>-Var</EM></DT>
<DD>A variable.
</DD>
<DT><EM>-Rest</EM></DT>
<DD>A term unifying with a list of domain variables or integers.
</DD>
<DT><EM>+List</EM></DT>
<DD>A list of domain variables or integers.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used in the labeling procedures.  When we look for the
   instantiation of a list of domain variables which is consistent with a
   set of constraints, it is better to start with instantiations which are
   most likely to fail, because this will cut down the size of the search
   space considerably.  The predicate deleteffc/3 selects among the
   variables with the smallest domain that one which has most constraints
   attached to it.  This choice is based on the heuristics that variables
   with more constraints are more likely to fail when instantiated.

<P>
   If several variables are equally eligible, the leftmost one in the
   list is taken.  Constants are treated like variables of domain size
   one with no constraints attached.  The list Rest is the same as
   List except that the selected element is missing.  In particular,
   any existing list order is preserved.

<P>

<H3>Fail Conditions</H3>
   Fails if List is nil.


<H3>Resatisfiable</H3>
   No.
<H2>See Also</H2>
<A HREF="../../lib/fd/constraints_number-2.html">constraints_number / 2</A>, <A HREF="../../lib/fd/deleteff-3.html">deleteff / 3</A>, <A HREF="../../lib/fd/indomain-1.html">indomain / 1</A>, <A HREF="../../lib/fd_search/search-6.html">fd_search : search / 6</A>
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